Vector-valued intensity measures for pulse-like near-fault ground motions

A vector-valued intensity measure (IM) is shown to account for the effects of pulse-like near-fault ground motions. This class of ground motions, which are indicated by the presence of a velocity pulse, can cause large responses in structures and their effects are not well described by traditional intensity measures such as spectral acceleration at the structure’s first-mode period, Sa(T1)Sa(T1). It is seen that the period of the velocity pulse is an important parameter affecting structural response, and a vector intensity measure which combines Sa(T1)Sa(T1) with a measure of spectral shape is much more effective at accounting for the effects of this pulse period. By performing probabilistic seismic hazard analysis for this IM and combining the results with predictions of structural response as a function of the IM, it is possible to account for near-fault effects when assessing the reliability of structures located at sites where pulse-like ground motions may occur.